US20040152935 discloses a method and system for reducing the formation of metal catalyzed side-reaction byproducts formed in the feed vaporization and introduction system of a methanol to olefin reactor system by forming and/or coating one or more of the heating devices, feed lines or feed introduction nozzles of/with a material that is resistant to the formation of metal catalyzed side reaction byproducts. The invention also may include monitoring and/or maintaining the temperature of at least a portion of the feed vaporization and introduction system and/or of the feedstock contained therein below about 400° C., 350° C., 300° C., 250° C., 200° C. or below about 150° C. The temperature can be maintained in the desired range by jacketing at least a portion of the feed vaporization and introduction system, such as at least a portion of the feed introduction nozzle, with a thermally insulating material or by implementing a cooling system. Said material that is resistant to the formation of metal catalyzed side reaction byproducts is preferably stainless steel such as AlSI (American Iron and Steel Institute) 316.
WO2007102916 relates to a process for producing light olefins from oxygenates wherein internal reactor surfaces are protected from metal-catalyzed coking preferably by employing a protective layer. A specific embodiment of this prior art is a process to convert a feed stream comprising an oxygenate in the reaction zone of a fast-fluidized-bed reactor at conversion conditions in the presence of a catalyst to yield a product stream comprising light olefins, wherein the one or more of the internal surfaces of the reaction zone comprises a protective layer resistant to metal-catalyzed coking. In this prior art is explained that metal-catalyzed coking leads to the formation of filamentous carbon, which promotes corrosion of reactor walls and coking of the catalyst. The carbon fibres may effect obstruction or clogging of moving parts (e.g., valve hinges) and increased pressure drops or even plugging of restricted spaces (e.g., diplegs). Metal-catalyzed coking also may be associated with carburization, although examination of iron surfaces exposed to conditions related to the present invention indicates that filamentous carbon is the principal concern. The protective layer may be formed on the one or more of the internal surfaces of the reaction zone. Effective materials can be selected from one or more of, tin, chromium, antimony, aluminum, germanium, bismuth, arsenic, gallium, indium, lead, copper, molybdenum, tungsten, titanium, niobium, zirconium, tantalum, hafnium, silver, gold, platinum, and mixtures, intermetallic compounds and alloys, as well as silicon and alumina. Preferred metals are selected from one or more of the group consisting of tin, chromium, nickel, antimony, aluminum, germanium and silicon. The metal-containing coatings can be applied by painting, electroplating, cladding, spraying, chemical vapor deposition, and sputtering. Preferably, the paint is a decomposable, reactive, metal-containing paint which produces a reactive metal which interacts with the reaction-zone internal surface. In a further alternative embodiment, one or both of aluminum and silicon can be applied to metal surfaces such as steels by well known deposition techniques.
A diluent can be mixed with methanol, said diluent is preferably steam.
It has now been discovered in the process of the previous prior art that not only coking is reduced but the undesired by-products such as CO, CO2, methane and hydrogen are reduced and that such reduction of undesired by products is amplified by the presence of an hydrocarbon fed with the methanol.
It has been observed, in addition of the MTO reaction to produce olefins, a reforming of the methanol catalyzed by the inner surface of the reactor. Said reforming is significantly increased when ethylene or other hydrocarbon is co-fed with methanol in the MTO reactor over zeolite or phosphated zeolite.
It seems that this reforming of methanol is increased when the catalyst has been regenerated in the reactor. Without being binded by an explanation the inventors think that during the regeneration which is e.g. a burning of the coke present on the catalyst by air or air enriched with oxygen the temperature in the reactor can reach 500 to 800° C. and then the inner surface of the reactor gets catalytic properties.
It was found that the injection of a small amount of DMDS could significantly reduce this effect due to sulfidazing the reactor walls. This reduction is amplified when ethylene or other hydrocarbons is co-fed with methanol in the MTO reactor.